A wide variety of irrigation systems are commercially available for use in watering crops, plants, and lawns. Sprinkler-based systems are generally the most popular, although systems that deposit water directly on the ground are also utilized, such as drip systems. In either case these systems are often automated so that they irrigate an associated area on a periodic basis without substantial human intervention.
Automated systems typically comprise an electronic controller and solenoid valve electrically coupled to the controller. The solenoid valve is typically located inline with a pressurized source of water. In operation, the valve opens to allow water to flow from the source, through a conduit, and out one or more sprinkler heads or drip emitters. When the cycle is complete, the controller signals the solenoid valve to close. Typically, these systems operate no more than a few times in day. A typical watering cycle may last anywhere from a few minutes to more than an hour.
After a watering cycle has been completed, it is not uncommon for the ground to be soaked and saturated. In the intervening period between cycles, the soil can become arid, especially in hot and dry climates. Both saturated and arid ground conditions can be damaging to certain types of plants. For instance, a seedling without a developed root system can be dislodged from the soil if enough water is added to the ground to cause puddling. Additionally, if the ground around a seedling is allowed to dry completely for even a short period of time the seedling can quickly dehydrate and die. Furthermore, there are types of plants that have root systems that are very intolerant of saturated soil conditions and can be damaged if exposed to saturated soil on a regular basis.
Ideally, it would be desirable to maintain soil at a predetermined and constant moisture level that is ideal for the plants growing therein. Increasing the frequency of irrigation cycles while reducing the time there between helps to maintain the soil at a more constant moisture level, but most electronic controllers are designed only to open an associated solenoid at most a few times every day. Even if controllers were available that allowed frequent watering cycles of short duration, the electronic solenoids generally available for use in sprinkler systems are not designed for continuous repetitive duty.
Another drawback of electronic systems is that they require coupling to an electrical power source that may not be conveniently available. Additionally, the conduits of electrical current, such as the wires between the solenoid and the controller, must be protected from moisture and other potential sources of damage. These requirements of traditional automatic systems make them complicated and consequently difficult and expensive to install.
Another problem that traditionally affects farmers and home gardeners alike is damage done to plants and crops by animals. It can be appreciated that animals in general will not bother plants or crops while a sprinkler is in operation because either they do not like the water or they are scared by sprinkler noise. Traditional sprinklers are relatively effective in deterring animals from entering an area being irrigated. Unfortunately, traditional sprinklers cannot be left on continuously for extended periods of time because of the amount of water used and the potential saturation of the underlying soil. Other objects, such as scarecrows, have very little effect on most animals. There are solutions that can be applied to the surfaces of plants that make them undesirable to animals, although the nature of the solutions often preclude there use on crops that are to be consumed by humans.